By default the UserManager uses session storage for its authentication
credentials. That is restricted to a single tab. In order to support
using the same auth token in multiple tabs, we could switch that to
localStorage which is shared by all tabs of the same domain. But then
if a user exited the browser, they might be surprised to find that they
were still logged in when restarting. The typically short lifetime of
OIDC tokens mitigates that somewhat, but it's probably best not to
subvert that expectation anyway.
Instead, we can continue to use session storage by using a BroadcastChannel
to notify other tabs of login/out events and transfer the token info as
well. This is a standard feature of modern browsers, but we're using
a library that wraps it for two reasons: it supports older browsers
with compatability workarounds if required, and it implements a leader
election protocol. More on that in a minute.
We would also like to automatically renew tokens shortly before they
expire. The UserManager has an automatic facility for that, but it
isn't multi-tab aware, so every tab would try to renew at the same time
if we used it. Instead, we hook into the UserManager timer that fires
about one minute before token expiration and use the leader election to
decide which tab will renew the token.
We renew the token silently in the background with a hidden iframe. In
this case, instead of using our normal auth callback page, we use a much
simpler "silent callback" which does not render the rest of our application.
This avoids confusion and reduces resource usage.
This also moves any remaining token lifecycle handling out of the Auth
component and into ZuulAuthProvider, so the division of responsibilities
is much simpler.
Change-Id: I17af1a98bf8d704dd7650109aa4979b34086e2fa
560fa563db